(1) Field of the Invention
This invention relates to novel pyridylthiazolidine carboxamide derivatives and salts thereof which have platelet activating factor (PAF) antagonizing activity and further relates to their intermediates.
(2) Description of the Related Art
PAF is a chemical substance released from human and other animal cells and is an acetylglyceryl ether of phosphorylcholine as represented by the following formula: ##STR2## wherein l is the integer 15 or 17.
PAF is physiologically active and causes contraction of the airway smooth muscle, increased vascular permeation, platelet aggregation and blood pressure fall and the like. It is thought to be a factor inducing asthma, inflammation, thrombosis, shock and other symptoms. Therefore, studies of substances capable of antagonizing the physiological activities of PAF are underway and several anti-PAF agents have been reported (e.g. European patent application No. 178,261 (A), U.S. Pat. Nos. 4,539,332, 4,656,190 and 4,621,038, European patent No. 115,979 (B) and British patent application No. 2,162,062 (A)).
The present inventors found that novel pyridylthiazolidine carboxamide derivatives differing in chemical structure from the known anti-PAF agents have an excellent anti-PAF activity and that novel N-substituted piperazine derivatives are useful as intermediates for preparing the pyridylthiazolidine carboxamide derivatives afore-mentioned. Based on this finding the inventors have now completed the present invention.